Here are four reasons Morgan Stanley analysts say McDonald's and other restaurants are struggling to revive sales.

1. Economic and political uncertainty.

In a controversial election year, many Americans feel uncertain about what the future holds. Fear over what will happen to the economy under a new president is making them more conservative with their dollars. When people are trying to save money, extras like restaurants are one of the first things they give up.

2. Gap between grocery-store and restaurant prices.

With the advent of private-label products, it's becoming increasingly cheaper to shop at the grocery store.

McDonald's CEO Steve Easterbrook says this has led to people eating at home instead of hitting up the drive-thru.

"There is a widening gap between food away from home and food at home, where the commodity decreases are being passed through by the grocers," Easterbrook said on Tuesday on a call with analysts."So the food at home, there's value to be had for families there, whereas eating out, there is a price-inflation environment."

Business Insider/Hayley Peterson

3. "Deal fatigue."

The major fast-food chains have all announced tantalizing deals this year.

McDonald's McPick 2 promotion lets customers get two items for $5.

Wendy's has been offering a "4 for $4" meal that includes a junior bacon cheeseburger, four chicken nuggets, small fries, and a drink, and KFC has a similar offering called the "$5 Fill Up" meal.

Burger King also launched another bundled promotion earlier this year, a "5 for $4" deal.

But while these deals initially got consumers in the door, they are now losing their luster.